Originally Red was Democrat and Blue was Republican. It was changed by the media in the 2000 election cycle because Blue elicited calm feeling and red more confrontational feelings. It was done to aid the Democrats like everything else the media does.
It was changed in 1992 by ABC. I know because I was screaming at the television when I noticed it. 1992 was the year that Bill Clinton, the Russia visiting, behind the Iron curtain touring, being the guest of prominent communist officials in the late 1960s, bastard was running for the Presidency.
Making him "red" made his links to communism all too apparent.